1. Field of the Invention
The present invention relates generally to framing tools and more specifically to a universally applicable framing square comprising calculated indicia and alignment marks for use with constructing equal and unequal pitched intersecting framing structures under any measurement system.
2. Discussion of Background Information
Developed over 100 years ago, the standard framing square rafter table provides a builder with calculated values for determining only 4 basic pieces of information: 1) length of common rafter, 2) length of hip and valley rafters, 3) the side cuts for the hip or valley and jack rafters, and 4) the difference in length for jack rafters for two distances between rafters: 16 inches and 24 inches.
Standard rafter squares typically comprise two flat, elongated arms—the body and the tongue—oriented at 90 degrees to one another and bearing incremented scales in inches. These scales enable carpenters to compute rafter lengths and rafter cut angles. The body scale indicia typically represent the run of the rafter wherein one (1) foot (i.e. 12 inches) represents the standard base run. The corresponding rise is specified on the opposing tongue as inches of rise per foot of run. A carpenter readily may identify locations for accurate level seat cuts and vertical plumb cuts by laying the square on the side of a beam, aligning the 12 inch mark on the body scale with the edge of the top face of the beam, and aligning with the edge of the beam the tongue scale number representing the ratio of the rise to the span (inches of rise per foot of run). Once the body and tongue are aligned, the carpenter may mark lines along the edges of the body and tongue respectively to indicate cut lines for seat and plumb cuts.
Some framing squares comprise various tables imprinted on the blades for use in calculating other construction measurements. Typically, these articles provide rudimentary tables for use with determine rafter lengths, board feet and diagonal brace lengths. For example, U.S. Pat. No. 247,353 to Howard teaches a square incorporating a useful rafter table for computing common rafter lengths. This table, printed on the front face of the square, provides rafter lengths for the standard roof pitches of one-fourth, one-third and one-half, based on a particular building span. Not only is this table limited to three common pitches, the square provides no information for determining measurements related to hip and valley formation. By comparison, U.S. Pat. No. 679,455 to Nicholls teaches a square incorporating a more robust rafter table containing computations for determining common rafter lengths for rise over run ratios of 2/12 to 18/12 and perhaps more ingeniously, this square provides tables for determining hip and valley rafter lengths.
These squares and others provide limited information, and all require additional complex calculations to determine angles and lengths at which to cut framing members, especially those forming compound joinery. In particular, these standard squares provide limited tabular information, and the measurement and alignment scales marked on the faces of these tools fail to address a large range of unequal pitches required during the design and building of unequal pitched roofs, for example. Some squares comprise complicated hinge mechanisms in an effort to improve usability; these tools, however, are less reliably “square” and nonetheless still limited to the scant markings on the face of the body and tongue. None of these existing squares has provided a wide breadth of precise calculations and alignment indicia requiring little computational effort on the part of the user to measure and cut lengths and angles during the formation of compound joinery.
Furthermore, in addition to the limited information provided to a builder, all existing squares are limited for use with either a standard measurement system (e.g. inches) or a metric system. None are universally applicable to both standard and metric units of measurement. Those squares that address metric systems are complex and cumbersome and require substantial additional calculations, which can result in computational errors and irreversibly incorrect cuts in framing members.
A need therefore exists for a framing square comprising tables and measurement indicia applicable to both imperial and metric units to be applied with equal accuracy, and wherein the tables eliminate any need for conversions. These tables include complete angular and dimensional information for common pitch and equal pitched hip and valley systems and also unequal pitched hip and valley systems.